Does carbon fibre in a board make it stronger or just change the characteristics of the board?
I have the choice between a standard wood core board or a carbon fibre top and bottom with wood core - I'm looking for more resistance to hard landings
Carbon increases the stiffness yet not the ultimate tensile strength,
The net result is an equivalent THICKNESS of carbon vs glass skin at the same fiber/resin ratio on the same core,
The carbon version will
a)be MUCH stiffer,
b)be considerably lighter
c) fail under similar static force (think hanging a weight on it)
d) fail with considerably LESS energy absorption compared to the glass during rapid bending in impact or landing (toughness)
Unless weight is pushing your board goals (which it is not) I would highly recommend staying with fiberglass, if you have the choice, S-glass has the best toughness properties of virtually any composite materials which is most relevant for kiting.
Carbon increases the stiffness yet not the ultimate tensile strength,
The net result is an equivalent THICKNESS of carbon vs glass skin at the same fiber/resin ratio on the same core,
The carbon version will
a)be MUCH stiffer,
b)be considerably lighter
c) fail under similar static force (think hanging a weight on it)
d) fail with considerably LESS energy absorption compared to the glass during rapid bending in impact or landing (toughness)
Unless weight is pushing your board goals (which it is not) I would highly recommend staying with fiberglass, if you have the choice, S-glass has the best toughness properties of virtually any composite materials which is most relevant for kiting.
You just forgot to mention that the price of carbon will be higher, mainly due to marketing.
I think the answers I've read don't take into account the many factors that are generally referred to as "carbon fiber". There are lots of misunderstandings and many more oversimplifications of the materials. I find that most of the carbon fiber in kiteboards right now is barely scratching the surface of what the materials can do if they are truly understood and used properly. The type of fiber is one thing, the layup is another, and the resin is another. Here is just a sample comparing two types of carbon fibers.
"first think about two characteristics which direct material choice. They are Strength and Stiffness. Strength is defined here as the amount of force that can be applied to material before it breaks (fails). Often mistakenly interchanged with strength, think about stiffness as the amount a material deforms when a given force is applied. A stiffer material will deform less under the same force compared to a less stiff material.
Modulus (more specifically Young’s Modulus) is the engineering term for stiffness of a material. When asked to explain the idea of modulus, or stiffness, we often employ some basic household items: a rubber band, and a length of dry spaghetti. Using the terms above, the rubber band is very strong because is it easily bent out of shape without yielding (permanently deforming), and will return to its original shape when the force is released. A rubber band is very hard to break, but is very flexible as it takes very little force to deform it. The uncooked spaghetti noodle however, is the opposite. It is very stiff as it resists deformation until it ultimately snaps suggesting that it is not very strong. Think of the rubber band as low modulus and the spaghetti as high modulus carbon fibers. The bragging rights associated with the use of high modulus fibers suggests that the bike is super stiff. However; remember what happened to the spaghetti noodle? High modulus carbon fiber may be stiff, but it is not very strong and thus--like the pasta--breaks with less force than lower modulus fibers. Simply put: fibers that are higher modulus (stiffer) are also weaker, and ones that are lower modulus generally offer higher strength (harder to break). It is also important to note that higher modulus fibers cost much more than lower modulus fibers, over 10 times more in some cases."
It is probably best to refer to specific boards rather than carbon fiber in general.
I used to build all my boards before I switched 100% to strapless surfboard rifing.
I used used carbon fiber in order to reduce weight bu to mantain propper flex I had to sacrifice board thickness (beam web height).
Carbon board should allways be about 60% thinner than coparable S-Glss boards in oreder to mantain the same flex.
lower modulus, home-made pasta also tastes better.
It's also interesting the carbon often goes in a woven fabric, in a lower modulus epoxy sauce.
In some cases, the shape of the noodle is key, and as often said before, sometimes it's the sauce that makes the meal.
I prefer fresh ingredients and a simple, small amount of sauce myself.
Don't disregard carbon too hastily.......I too was against it and felt it was marketing and unnecessary bling. I've since changed my tune. I know mountain bikes and kiteboards are two totally different animals, but carbon used to in the right application (layup, resin, modulus) can't be beat for strength to weight ratios.
This video will give you some idea of just how strong carbon is. I rode a Santa Cruz Blur LT aluminum all summer long and loved it. I then bought a carbon SC Blur LT and it was significantly better. Lighter, stiffer, more responsive, etc. I wouldn't dream of riding a fiberglass mountain bike......
This is impressive stuff.
Now when it comes to kiteboards, I would be quite skeptical. I know many companies say "CARBON" on the board but only have small reinforcement strips or cosmetic topsheets/bases to give the cool look. But most of these boards are still 90% WOOD. I haven't tried a Carved carbon yet, but I think Bro-kite and Carved are the only two that are full on carbon, no wood core.
BWD wrote:...
It's also interesting the carbon often goes in a woven fabric, in a lower modulus epoxy sauce.
....
And a Complete Waist of materials it is , when carbon is Woven .
It may look cool, but 30% of it's properties go Byby, the moment
it's woven.
Carbon + Kevlar or Spectra UNI , is about as Good as it gets ;
Boron is better ; but that stuff can Kill Ya !!
Bille
You are correct in terms of bending and buckling. when you've gotta carry stress in a direction, uni is the way to go.
That stated weave and inherent waviness is quite beneficial in off axis loading (perpendicular to the fibers) and impacts
if you have a softer core that your trying to keep from putting your foot through (like a kiteboard) or some highly stressed uni that can't get stone damage. Or simpler yet trying to keep your trophy wife's stiletto heels from going through the floor boards of your exotic car, those basket weaves can be beneficial while still providing useful stiffness that Kevlar would not. and it does it while looking awesome....which of course saves the weight of paint, (for those of you who are functionally obsessed.)
You'll usually see most suspension components on race cars finished with a layer or 2 of carbon weave. This is more than cosmetic.
Anyway back to the original topic, he wants better resistance to hard landings.
Wood core,( for the off axis loading) S-Glass for energy absorption during bending
